SAVAR, Bangladesh (AP) -- Rescue workers in Bangladesh have given up hope of finding any more survivors in the rubble of a building that collapsed five days ago, and have begun using heavy machinery to remove the rubble and look for bodies, an official said Monday.

At least 380 people were killed when the illegally-constructed, 8-story Rana Plaza collapsed in a heap on Wednesday morning, with thousands of workers in the five garment factories in the building. About 2,500 survivors have been accounted for. The building owner, Mohammed Sohel Rana, was arrested Sunday in the western border town of Benapole while allegedly trying to flee to India.

The collapse was the deadliest disaster to hit the garment industry in Bangladesh that is worth $20 billion annually, supplies global retailers and is a mainstay of the economy.

Volunteers, army personnel and firemen have worked around the clock since Wednesday, mostly using hands and light equipment to pull out survivors. Around midnight Sunday, authorities deployed hydraulic cranes and heavy cutting machines to break up the massive slabs of concrete into manageable segments that could be lifted away.

"We are proceeding cautiously. If there is still a soul alive, we will try to rescue that person," said army spokesman Shahinul Islam.

"There is little hope of finding anyone alive. Our men went inside and saw some dead bodies in the ground floor. But no one was seen alive," said Brig. Gen. Ali Ahmed Khan, the chief of the fire brigade at the scene.

Gone are the civilian volunteers who had swarmed the site since the disaster and crawling over the wreckage. Only army soldiers in green camouflage and hard hats were visible, watching heavy machinery digging into thick concrete. Gone also were the waiting ambulances that over the past five days had rushed the rescued to hospitals.

Prime Minister Sheikh Hasina visited the site and a nearby hospital to meet with survivors on Monday, the first time since the disaster.

Hasina had ordered the arrest of building owner Rana, a small-time political operative from her Awami League party's youth wing. He was brought back by helicopter from the border town to the capital, Dhaka, where he is expected to be charged with negligence on Monday.

He had permission to build a 5-story building but added three more illegally. He last appeared in public Tuesday in front of the Rana Plaza after huge cracks appeared in the building.

Witnesses said Rana assured tenants that the building was safe. Police, however, ordered an evacuation. A bank and some first-floor shops closed, but managers of the garment factories on the upper floors told workers to continue their shifts.

Hours later, the Rana Plaza was reduced to rubble, crushing most victims under massive blocks of concrete.

Police have also arrested four owners of three factories. Also in detention for questioning are two municipal engineers who were involved in approving the building's design. Local TV stations reported that the Bangladesh High Court has frozen the bank accounts of the owners of all five garment factories.

A garment manufacturers' group said the factories in the building employed 3,122 workers, but it was not clear how many were inside when it fell. About 2,500 survivors have been accounted for.

The death toll surpassed a fire five months ago that killed 112 people and brought widespread pledges to improve worker-safety standards. But since then, very little has changed in Bangladesh.

The collapse and previous disasters in garment factories have focused attention on the poor working conditions of workers who toil for as little as $38 a month to produce clothing for top international brands.

Its garment industry was the third-largest in the world in 2011, after China and Italy, having grown rapidly in the past decade.

Among the garment makers in the building were Phantom Apparels, Phantom Tac, Ether Tex, New Wave Style and New Wave Bottoms. Altogether, they produced several million shirts, pants and other garments a year.

The New Wave companies, according to their website, make clothing for several major North American and European retailers.

Britain's Primark acknowledged it was using a factory in Rana Plaza, but many other retailers distanced themselves from the disaster, saying they were not involved with the factories at the time of the collapse or had not recently ordered garments from them.

Wal-Mart said none of its clothing had been authorized to be made in the facility, but it is investigating whether there was any unauthorized production.

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